border-1px($color)
    position: relative
    &:after
        display: block
        position: absolute
        left: 0
        bottom: 0
        width 100%
        border-top: 1px solid $color
        content: ' '

bg-image($url)
   background-image:url($url+"@2x.png")
   @media (-webkit-min-device-pixel-radio: 3),(min-device-pixel-radio: 3)
      background-image: url($url + "@3x.png")
